The purpose of this study was to investigate the presence of a practice effect on the Wingate anaerobic test (WAnT). Twenty-five young adult men (mean age = 20 years) performed 2 trials of the WAnT, which were separated by 7 days. Mean peak power (PP) and mean power (MP) for trials I and II were compared using a 1-way repeated measures analysis of variance to determine if a practice effect existed. Mean PP and MP scores were significantly higher (p < 0.025) on trial II (867.64 and 634.68 W for PP and MP, respectively) than on trial I (764.48 and 604.92 W), indicating that a practice effect occurred. Effect size (Cohen's d) for PP and MP was 0.72 and 0.35, indicating a large effect and small effect, respectively. Therefore, at least 1 full administration should be performed prior to a baseline power output measurement.
Background: In female athletes, the knee is one of the most commonly injured areas of the body. Uncontrolled frontal plane knee motion or "valgus collapse" has been identified as a risk factor for knee injury. This movement pattern has been observed in cases of anterior cruciate ligament (ACL) tears in athletes and it has also been linked to the development of patellofemoral pain syndrome. While often seen during a body-weight squatting maneuver, the valgus collapse is magnified when the athlete either lands from a jump or attempts to accelerate into a jump. Knee injury prevention programs that emphasize knee separation have shown the ability to reduce the effect of the loss of valgus control and are associated with a decrease in knee injury risk. Purpose: The purpose of this study is to examine the impact of hip elastic-resisted neuromuscular feedback on frontal plane knee abduction during a counter jump maneuver. Design: Randomized, controlled repeated measure. Methods: In total, 20 female volleyball athletes (mean age, 16.4 6 1.6 years; age range, 15-18 years) were included in this study under the following condition: athletes should have had a pain-free dysfunctional squatting pattern with no signs of structural dysfunction. During a drop-jump test, the distance between the hips, knees, and ankles was measured via video analysis software. The separation distance between the knees (mid-patella width) and ankles (lateral malleolus width) was normalized by the hip separation (greater trochanter width) distance and measured at pre-landing, landing, and takeoff. Athletes were randomized into either a control group or a neuromuscular intervention group; a SquatGuide was used and variable resistance was manually applied to the distal femur to resist hip abduction by means of an elastic band. Before a volleyball practice session, the athletes in the neuromuscular intervention group performed 30 repetitions of a deep squat with variable resistance manually applied around the distal thighs; the SquatGuide was used to provide feedback on proper lower-quarter positioning. During this period, the control group did not participate in any activity. The jump landing characteristics of both groups were immediately re-examined before practice and again at 60 min at the conclusion of practice. Results: The means and standard deviations for the absolute distances (measures in centimeters) of knee and ankle separation and for the normalized knee and ankle separation were calculated. There was no correlation between the distance in the knee and ankle separation for each of the jump-land sequences. After squat training, statistically significant increases were found in the absolute distance (P < .001) and the normalized knee and ankle separation distance (P < .001) for all phases of the jump-land sequence, both immediately following the training and at 60 min after training.
Background:Segmental rolling has been utilized as an assessment and intervention tool to identify and affect dysfunction of the upper quarter, core, and lower quarter. One theory to explain dysfunctional segmental rolling is a lack of segmental spinal control / stabilization. Faulty muscle firing sequencing has been related to poor spinal stability, however to date, no assessment tool exists to evaluate a patient's motor coordination of local and global musculature. Purpose:The purpose of this study was to assess the temporal sequence of lumbar multifidus activation associated with anterior deltoid activation, and to determine if faulty sequencing was associated with the inability to segmentally roll in subjects without mobility restrictions. The authors hypothesized that in individuals who could not roll, a multifidus muscle onset latency relative to a prime mover activation would be present. In addition, a subset of the individuals with an inability to roll were utilized for a pilot study examining the ability to address the firing pattern with corrective exercise.Methods: Twenty healthy subjects (13 females, 7 males), ages 19-25, participated in the study. Each subject underwent an upper and lower quarter screen and assessment of thoracic spine mobility. Subjects were excluded from the study if they had previous spine surgery, or were currently experiencing back pain. In addition, subjects who had any disease, disorders, or pathology that would hinder participation in segmental rolling or who had spinal movement contraindications were excluded. Since shoulder flexion is performed during the study, participants who had shoulder pathology or contraindications to upper extremity movement were excluded as well. Subjects with less than 50 degrees of trunk rotation were excluded from the study due to a possible physical mobility limitation that would prevent proficient segmental rolling. Included subjects were assessed on their ability to segmentally roll. Subjects who could complete the rolling task were placed in cohort A ("can roll"), and subjects who could not roll were placed in cohort B ("can't roll").Electromyographic (EMG) activity of the multifidus was recorded adjacent to the lamina of the L4 vertebrae using intramuscular fine-wire electrodes. EMG activity of the anterior deltoid was also recorded with a surface electrode during a single arm movement into shoulder flexion. While in a standing position, subjects were instructed to move their right upper arm into flexion as quickly as possible. Subjects flexed their shoulder to 90 degrees for three trials while muscle activity was recorded. Data were high-pass filtered at 30 Hz to remove baseline artifact, and the onset EMG times was selected as the point at which EMG increased two SD above baseline levels. Onset of the multifidus muscle was reported relative to that of the prime mover (anterior deltoid). Muscle onset latency was defined as the time difference between the onset of contraction of the multifidus and the anterior deltoid.Results: Nine subjects ...
Background/Purpose: Studies investigating the trends of anterior cruciate ligament (ACL) reconstruction rates have shown that since 2006, females aged 13-17 years of age have had the highest injury rates of any age or gender group in the country. This study investigated the lower chain biomechanics of landing before and after a six-session training intervention. This training session was conducted between the fall and spring season break for a travel soccer club. Study design: Non-randomized controlled follow-up study. Methods: Thirty-six healthy, female soccer players between the ages of ten and fifteen years old participated. Using an inertial tracking system for three-dimensional kinematic (motion) analyses of a drop jump assessment that were conducted before and after a six-session training intervention focused on proximal hip strengthening, motor control, and lower extremity loading strategies. The study took place over a period of eight weeks. Results: When compared to pre-intervention measures for the drop jump, post-intervention measures were significantly improved bilaterally for each of the following variables: knee flexion (p = 0.000), hip flexion (p = 0.000), and hip abduction (p = 0.002. As compared to pre-test jump height, post-test jump heights were significantly lower by an average value of 1.8034 cm (p = 0.005). Conclusions: The results of this study showed that a short duration (six, 90 min, sessions occurring over 8 weeks) training intervention can significantly influence the landing
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